1. Field of the Invention
The invention relates to a secondary battery provided with a current interrupt device, and a manufacturing method of this secondary battery.
2. Description of Related Art
A secondary battery described in Japanese Patent Application Publication No. 2008-66254 (JP 2008-66254 A) is provided with a current interrupt device. A current path is interrupted by interrupting foil that forms a portion of the current path breaking when a diaphragm deforms by a predetermined amount or more in response to internal pressure of an exterior body.
When manufacturing the secondary battery described in JP 2008-66254 A, an external terminal, a gasket, a sealing body, an insulation holder, and a sealing lead are overlapped in this order from a side that will be on the outside in the exterior body. One end side that is positioned inside of the exterior body, of the external terminal that has been inserted through a through-hole formed in the sealing body is crimped. As a result, the gasket is fixed compressed between the external terminal and the sealing body, and the insulation holder is fixed compressed between the sealing body and the sealing lead. In this state, the diaphragm is laser welded to a peripheral edge portion of the sealing lead.
Here, in the secondary battery described in JP 2008-66254 A, a metal member with relatively high thermal conductivity such as aluminum is used as the sealing lead and the external terminal, and a resin member with relatively low thermal conductivity and good insulating properties such as polyether ether ketone is used as the insulation holder member. Therefore, heat generated when welding the diaphragm to the sealing lead is transferred to the gasket via a rivet member and the external terminal.
If excessive heat is transferred to the gasket, the temperature of the gasket will exceed a glass transition point of the material of the gasket, and the gasket will rupture or deform, reducing the sealability of the inside of the exterior body. Also, the elasticity of the gasket may decrease from the effect of the heat, which may result in the external terminal, the sealing lead, and the holder member and the like rattling and vibrating. This rattling may unintentionally cause a break in the current path. If the performance of the gasket that keeps the inside of the exterior body airtight decreases, the reliability of the secondary battery will suffer.